The present disclosure relates generally to masking articles, such as masking tape, and, more particularly, to a masking article that produces precise paint lines, and to adhesive compositions for making masking articles.
When applying a surface coating, such as paint or stain, to a surface, care must be taken so that the paint does not get on the surfaces adjacent to the surface to be painted. This can be accomplished by carefully painting the surface, or by masking off the area around the surface to be painted. Masking articles, such as masking tapes and adhesive masking sheets, are often used to protect the area adjacent to the surface being painted. When using such masking articles, it is generally desirable that the paint not bleed past the demarcation line defined by the edge of the masking article. In this manner, the masking article will produce a paint line between the painted surface and unpainted surface that is smooth and consistent, and precisely matches the line intended by the user. Depending on a number of factors, such as how well such masking articles are applied to the surface, the energy of the surface, and the texture of the surface to which such masking articles are applied, paint may flow beyond the edge of the masking article and under certain regions of the masking article, thereby producing an imprecise paint line.
Adhesive tapes and masking materials having an edge coating for improving the masking ability of the materials are known in the prior art. U.S. Pat. No. 6,828,008 (Gruber), for example, discloses an absorbent edge coating for masking tape and other masking materials. The masking tape comprises a substrate having a top surface, a bottom surface, and at least one masking edge. The bottom surface of the substrate has an adhesive layer applied thereto. An absorbent edge coating is applied to at least one masking edge of the substrate so as to at least substantially prevent liquids addressed to the at least one coated masking edge from being absorbed into the substrate of the tape and from passing between the bottom surface of the tape and a surface to which the tape has been applied.
U.S. Patent Publication No. 2010/0307411 discloses an adhesive masking article for shielding a protected work surface from a coating applied to a surface adjacent the protected work surface, the masking article including a backing layer having first and second opposed major surfaces, and at least one edge. The masking article has an adhesive on at least a portion of at least one of the first and second backing layer opposed major surfaces and a water soluble cationic barrier inducing compound present on at least the edge of the masking article. The cationic compound contacts the coating when the coating comes into contact with the edge of the backing layer and destabilizes the coating, thereby producing a barrier effect.
Previous attempts to develop masking articles that impede the migration of paint past the edge of the masking article suffer from a number of drawbacks and disadvantages. For example, known adhesive masking articles may include the use of ingredients that are difficult to apply to the masking article during the manufacturing process, may require expensive packaging to maintain their effectiveness, may be harmful if ingested, and/or may cause skin, eye and nose irritation, which may require warnings and/or special handling instructions, or may produce unintended and undesirable effects at either the interface of the masking article and the paint, or on the surface to be painted.
Masking articles can include superabsorbent polymers (SAPs), such as sodium polyacrylate, as edge treatments. In addition, because of their absorbency, when masking articles including superabsorbent polymers are used in paint masking applications, an undesirable raised region, or ridge, of paint is often created along the edge of the masking article. This raised region generally takes longer to dry, and is therefore more susceptible to damage prior to fully drying. In addition, loose or excess SAP may fall onto the surface to be painted. SAP on the surface to be painted may, in turn, interfere with the application of paint to the surface (i.e. it may create an unsightly blotchy appearance in the paint).
Additionally, masking articles, such as adhesive tapes, having an edge coating suffer from certain inherent disadvantages. First, when a user divides the article, e.g. tears off a piece of tape, the new edge created by the division does not have the edge coating for preventing flow of paint beyond the edge of the masking article. Second, providing edge coatings necessitates a separate processing step in making the article or tape. Third, edge coatings almost inevitably cause differences in adhesion of the article to a given substrate at the edge vs. the remainder of the article. Increased adhesion can cause difficulty in removing the article from the substrate after paint is applied, can cause residual materials to be left on the substrate after removal, or both. Decreased adhesion can lead to egress of the paint during coating. A related issue is that edge coatings may suffer from lack of adhesion to the article itself, and may flake off, preferentially adhere to the substrate on which the article is applied, or otherwise depart from the article and thereby fail to provide the intended protection. Fourth, edge coatings represent a separate and, in some cases costly, additional step in processing. A related issue is that edge coatings are highly impractical to manufacture in any form but a straight-edged product, such as a tape. Manufacturing of masking articles such as stencils or other non-linear shapes is impracticable using edge-coating technology.
The need exists for adhesive masking articles that address the above listed limitations. Additionally, the need exists for an adhesive masking article for paint masking that is easy to make, does not require special packaging, is safe and easy to use, and produces sharp, clean, precise, smooth, even paints lines. The terms “sharp”, “clean”, “precise”, “smooth” and “even”, when used to describe a paint line, generally refer to a paint line that corresponds to and is defined by the edge of the masking article. That is, a sharp, clean, precise, smooth, or even paint line is one in which the paint does not extend significantly beyond the edge of the masking article so as to penetrate under the masking article. Thus, a “sharp”, “clean”, “smooth”, or “even” paint line has minimal or no paint bleed under the article (i.e. little or no paint flow between the masking article and masked surface).